KR101924246B1 - Method for hydraulically boosting an electric parking brake of a vehicle - Google Patents

Abstract

The present invention relates to a method for hydraulic boosting of an electric parking brake of a vehicle, the brake comprising at least one brake actuator (2c, 2d). The vehicle has a hydraulic service brake function and an electric parking brake function for electrically and hydraulically actuating the at least one brake actuator (2c, 2d), and the application force F ("F") electrically generated by the electric parking brake function Is overlaid on the brake actuators 2c and 2d by the boosting brake force generated by receiving the hydraulic boosting brake pressure P _u provided by the hydraulic service brake function. According to the present invention, when the parking brake is operated to generate a predetermined applied force, the applying force generated by the brake actuator (2c, 2d) is applied to a measuring variable (I) representing the value of the applying force actual values by the first target value representing a is detected as the (I _ist), the actual value (I _ist) is the applied to the first target power value of the force (F _{1, soll)} of the measured variable (I) (I _1, is less than _soll), is applied to a predetermined target boosting brake pressure value (P _u, hydraulically boosted brake pressure (P _u) that the brake actuator (2c, 2d corresponding to the _soll)), by the electric parking brake function , A tensile force adjusting function for adjusting the tensile force of the brake actuators (2c, 2d) receiving the hydraulic boosting brake pressure (P _u ) is performed to realize the predetermined applied force.

Description

METHOD FOR HYDRAULICALLY BOOSTING AN ELECTRIC PARKING BRAKE OF A VEHICLE FIELD OF THE INVENTION [0001]

The present invention relates to a method for boosting an electric parking brake of a vehicle according to the preamble of claim 1.

A combined vehicle brake including an electromechanically operable parking brake also known as a hydraulically operable service brake and a fixed brake is known from DE 102008051350 Al wherein the hydraulic working pressure chamber in the brake housing is coupled by a brake piston On the one hand, a hydraulic pressure medium can be applied to perform the service brake, and on the other hand, can be operated along the longitudinal axis of the piston by a non-reversible transmission to achieve a parking brake, Translates the motion into translational motion of the brake piston to perform the parking brake process and maintains the brake piston in the operating position by self-locking of the transmission.

Such a parking brake system also includes an electronic controller, which generally includes a driving dynamics controller (DDC) of the motor vehicle, and includes two known hydraulic and electrical components as well as two for the rear wheel of the motor vehicle And two full bridges for independent control of the two DC motors of the parking brakes.

In such a parking brake system, customer and safety requirements regarding price, performance, noise, stability, availability and comfort must be realized, which often conflict with each other.

This system design should therefore be chosen such that under a normal ambient atmosphere, for example the voltage of the electrical system of the onboard electrical system and the temperature of the electric motors of the parking brake, the required energizing force to reach the minimum value can be reliably applied. For cost reasons, the enforcement power is indirectly determined from other parameters indicating the enforcement power rather than directly measuring for this purpose. Thus, for example, in order to apply the above-described electric parking brake, a predetermined maximum or switch-off current of the electric motor is used as a switch-off criterion, whereby the target applied force of the threshold is realized as the target force value see.

However, this method can not guarantee a safe shutdown of the vehicle in all situations, for example, at an increased temperature and / or a lower operating voltage, since the desired switch-off current is no longer realized.

To solve this problem, for example, DE 10 2010 029 391 A1, which uses vehicle hydraulics in support of realizing the required enforceability, is known. For this purpose, prior to the application process for the parking brake, a hydraulic boost essentially determines whether the acceleration values of the wheels are used and the existing temperature values for the brake actuators are being used. According to the existing method according to DE 10 2010 029 391 A1, when the parking brake is operated, only after the pressure medium is initially taken from the front wheel brakes and delivered to accumulate the boosting brake pressure in the parking brakes for the rear wheels A hydraulic boosting brake pressure is generated so that the application of the parking brake is performed.

In the above conventional method of hydraulically boosting the parking brake function, it is necessary to determine whether the hydraulic boost is necessary before applying the parking brake. This has the disadvantage that the hydraulic boost is performed too often even if the hydraulic boost is not absolutely essential. This behavior represents a significant loss of comfort for the driver.

It is an object of the present invention to specify a method for a hydraulic boost of an electric parking brake of a vehicle of the type described above, by which the disadvantages can be avoided.

This object is achieved by a method having the features of claim 1.

A method according to the invention for the hydraulic boosting of an electric parking brake of a vehicle comprising at least one brake actuator, the vehicle comprising a hydraulic service brake function and an electrical parking brake function for electrical and hydraulic actuation of the at least one brake actuator And the application force electrically generated by the parking brake function is overlaid on the brake actuator by the boosting brake force generated by receiving the hydraulic boosting brake pressure provided by the service brake function, and according to the present invention, Characterized in that the applied force generated by the brake actuator is characterized as being detected as an actual value by a measuring variable indicative of its value and wherein the actual value of the measuring variable represents the first target force value of the applied force The brake actuator receives the hydraulic boosting brake pressure corresponding to the specified target boosting brake pressure value and the further applying function is such that the brake actuator, which receives the hydraulic boosting brake pressure, Is performed by a parking brake function which is additionally applied.

In the above-described method according to the present invention, the actual value of the measurement variable representing the application force, which preferably indicates the motor current of the electric motor of the parking brake, The hydraulic boost is performed only when the current limit value or the switch-off current value can not be reached. Also, since the brake piston has already been moved closer to the desired final position by the parking brake function, the expanded energy to produce the hydraulic boosting brake pressure is lowered.

A hydraulic pump is a means of generating pressure, which is used to generate a hydraulic boosting brake pressure in a clear way and controlled by a service brake function. Since the brake piston of the brake actuator has already been moved close to its final position by the parking brake function, the volume supplied by the hydraulic pumps remains very small, i.e. the energy consumption of the hydraulic pump is low.

In one embodiment of the present invention, the target boosting brake pressure value is set such that the resulting boosting brake force is set to a first target force value, i.e., a value corresponding to the required force, and the hydraulic boosting brake pressure corresponding to this target force value Following generation, the means of pressure generation is switched off, and the boosting brake pressure applied to the brake actuator is hydraulically limited in the brake actuator. In this way, the brake piston of the brake actuator receives the boosting brake pressure corresponding to the desired final value of the applied force so as to be able to perform further application.

According to another embodiment of the present invention, a limited boosting brake pressure is applied by the parking brake function until the actual value of the measurement variable of the applied force corresponds to a target value smaller than the first target value corresponding to the first target force value The subsequent additional application of the parking brake occurs by controlling the receiving brake actuator. Thereby, the target value can be selected such that the electric motor provided to start the micro-movement of the brake piston of the brake actuator, that is, to drive the brake actuator, performs some rotations. The high-speed smooth running of the brake actuator with respect to the brake discs is realized by the minute control of the brake actuator.

According to another embodiment of the present invention, the target boosting brake pressure value corresponds to a target inlet pressure value in which the resulting boosting brake force is smaller than the first target force value, and following generation of the hydraulic boosting brake pressure, Is not switched off, and the brake actuator continues to receive the generated boosting brake pressure. According to one development example, by adjusting the brake piston of the brake actuator subjected to the boosting brake pressure of the parking brake function to the position corresponding to the specific power application target using the stored displacement force characteristic, for the additional application of the parking brake, Control is subsequently activated. If the target position is not achieved with the brake piston by the further application of the parking brake by determining the actual position, an error message is generated to the vehicle driver.

According to one embodiment of the present invention, instead of the displacement control, an actual value of a measurement variable indicative of an applied force generated by a brake actuator during the application of the brake actuator by the parking brake function is detected, By completing the further application if it corresponds to the second target force value, a further application of the parking brake can also be performed, wherein the second target force value is equal to the first target force value by a force value corresponding to the boosting brake pressure . Preferably, in the above embodiment, an error message is also generated if the actual value of the measurement variable does not reach the second target value.

In a preferred manner, before performing further application using the second target value of the measuring station, the brake actuator subjected to the boosting brake pressure is subjected to a further application by this displacement control by a minute displacement quantity in the release direction of the parking brake Can be controlled to realize the defined position.

According to a preferred development of the invention, the hydraulic boosting brake pressure is reduced after performing the additional application function.

In order to perform the parking brake function, the brake actuator is driven by the electric motor, so that it becomes convenient to detect the motor current of the electric motor as a measurement variable indicative of the applied force.

The method according to the invention is described in detail below and with reference to the accompanying drawings. In the drawing,
Figure 1 shows a schematic block circuit diagram of a brake system for carrying out the method according to the invention.
Fig. 2 shows a schematic process diagram for explaining an exemplary first embodiment of the present invention.
Fig. 3 shows a schematic process diagram for explaining an exemplary second embodiment of the present invention.
4 shows a schematic process diagram for explaining an exemplary third embodiment of the present invention.

1 shows a brake system of a motor vehicle having a controller 20 of a driving dynamics control system (DDC system) to which sensor data of a DDC sensor 21 and status signals of a parking brake switch 10 are supplied. 1), wherein the application or release of the parking brake by the driver of the motor vehicle can be started with the parking brake switch 10. For this purpose, the controller 20 not only performs the service brake function by the brake system, but also carries out the parking brake function by controlling the components of the parking brake, which will be described below.

The controller 20 controls the brake system 1 and shows only the brake circuit I for the left front wheel 11 and the right rear wheel 12 connected to the brake cylinder (tandem master cylinder) 9 However, the second brake circuit II is also designed corresponding thereto and similarly, it is connected to the brake cylinder liner 9 and is shown only as an outline. The wheel brakes of the left front wheel 11 and the right rear wheel 12 having a brake caliper 2a or 2b are respectively connected to the brake circuit I via a hydraulic line in which the rear wheels 12, Is designed as a parking brake with an actuator 2c, and is operated by a direct current motor 2d independently of the application of hydraulic pressure.

In order to perform the parking brake function, the controller 20 is connected to the brake actuator 2c for controlling the DC motor 2d. The rotational motion of the direct current motor 2d is converted into the linear motion of the brake piston of the brake actuator 2c through the transmission so that the torque of the direct current motor 2d is applied to the brake caliper 2b through the brake piston as the applying force F . Following the switch-off of the motor current I, the generated applied force F is maintained due to the self-locking of the transmission.

The applied force (F) itself is not measured. When the parking brake is applied, the DC motor 2d is driven in the applying direction through the H bridge, that is, for example, by the controller 20 with a positive applied voltage. After the motor has run up, the current rapidly decreases to its minimum value, resulting in a so-called no-load current, while the maximum number of rotations is set. After the linings are in contact with the brake disks, i. E. After overcoming the air gap, the forces accumulate and the current increases. At this time, the brake piston of the brake actuator is driven by the DC motor 2d until the specified and defined target value I _soll of the motor current I reaches or exceeds the actual value I _ist . Then, the applying force F _soll associated with the corresponding current value I _soll is reached, and the DC motor 2d is switched off.

In order to set the applied force (F _soll) necessary, the motor current (I) of the direct current motor (2d) it is measured, by a controller 20 connected to a voltage bridge not represent H applied to the direct current motor, the direction necessary Lt; / RTI > is dependent upon whether an authorization or release is to be performed. When the defined target value I _soll of the motor current I reaches or exceeds the actual value I _ist , the direct current motor 2d is switched off. The target value here corresponds to the required applying force (F _soll ).

The target value I _soll of the motor current I is obtained by experimentally measuring the characteristics of the brake actuators 2c and _comparing the corresponding current value used as the target values I _soll to the characteristics of the controller 20 .

The position of the brake piston of the brake actuator 2c or the rotation number of the direct current motor 2d is similarly estimated by a predetermined model without being directly detected.

The brake system 1 includes a brake silander 9 and a brake booster 13 connected to the reservoir 5 for hydraulic fluid or brake fluid. The brake silencer 9 generates a brake pressure at the outlet which is connected to the brake booster 13 and corresponds to the brake pedal 16 driven by the driver. The brake pressure is supplied to the inlet valve 7a or 7b opened at the inlet side through the opened separation valve 15 so that the corresponding hydraulic brake pressure is applied to the front and rear wheels 12a and 12b by the brake calipers 2a and 2b 11 and 12, respectively. The two inlet valves 7a and 7b are normally open. The brake booster 13 having the brake master cylinder 9 is connected to the controller 20. [

A normally closed outlet valve 8a or 8b connects the brake calipers 2a or 2b to the low pressure reservoir 14 which is connected to the hydraulic pump 3 at the suction side And can be connected to the brake master cylinder 9 via a change-over valve 6. [

For example, to force the brake medium to be displaced in the low pressure reservoir 14 during pressure reduction, or to force the rear wheels 12 when triggering the parking brake, if the required application force (F _{e , soll} ) in order to generate a boosting hydraulic brake pressure (P _u), the hydraulic pump 3 is provided with the brake caliper (2a and 2b). The brake piston of the brake actuator 2c receives the hydraulic boosting brake pressure P _u and superimposes the applied force F _e electrically generated by the DC motor 2d.

The hydraulic pump 3 is driven by an electric motor 4 which is itself controlled by the controller 20 using pulse width modulation (PWM). The electric motor 4 is here controlled so that the hydraulic motor 3 can accumulate the brake pressure on the high pressure side in accordance with the drawing on the brake fluid at the suction side.

Therefore, during the control of the hydraulic pump 3 in the stepper motor mode, the brake fluid can be discharged out of the pressure chamber of the brake caliper 2a or 2b and the switching valve 6 and the inlet valve 7a or 7b are closed On the other hand, the outlet valve 8a or 8b is opened to make a connection to the pressure chamber.

A first exemplary embodiment of the present invention is described below with the process diagram according to FIG. 2 and the brake system according to FIG. The explanation related to the brake circuit I is also related to the brake circuit II.

F_{1, soll}). 따라서, 단계 S4 에서, 모터 전류 (I) 의 실제 값 (I_ist) 이 검출되고 목표 값 (I_{1 , soll}) 과 비교된다. 상기 목표 값 (I_{1 , soll}) 이 실제 값 (I_ist) 에 도달하거나 또는 초과하는 경우, 프로세스는 단계 S8 ("종료") 에서 종료한다.Following the detection of the shut parking brake switch 10 by the controller 20 in accordance with the start of the process (step S1: "start") and step S2 ("parking brake closure"), The application of the brake caliper 2b to the rear wheel 12 occurs in step S3 by the controller 20 that controls the DC motor 2d accordingly. The necessary applying force F _{1, soll} corresponds to the specified target value I _{1 , so 11} of the motor current of the direct current motor 2d (I _{1 , soll}

F _{1, sol 1} ). Thus, in step S4, the actual value I _ist of the motor current I is detected and compared with the target value I _{1 , soll} . If the target value (I _{1 , soll} ) reaches or exceeds the actual value (I _ist ), the process ends at step S8 ("end").

In other cases, the controller 20 determines whether or not the hydraulic boost, that is, the hydraulic boosting pressure P _u received by the brake piston of the brake actuator 2c, is in accordance with step S5 ("P _u generation & (3). The target value P _{u , soll} of the boosting pressure P _{u to} be generated here corresponds to the required applying force F _{1, soll} . The boosting brake pressure P _u corresponding to the target value P _{u , soll} is accumulated only in the parking brakes of the rear wheels 12. The inlet valve 7b is opened and the outlet valve 7a of the brake caliper 2a is closed on the front wheel 11 side and the outlet valve 8b of the brake caliper 2b of the rear wheel 12 is closed, Is also kept closed. Following this accumulation of pressure in the parking brakes, the hydraulic boosting brake pressure P _u is limited within the brake actuator 2c by closing the inlet valve 7b. The hydraulic pump 3 is then switched off.

Subsequent to step S6, a direct-current motor the motor current (I) the first target value (I _{1, soll)} than the parking brake by controlling the direct current motor (2d) until it reaches the lower target value (I _{2, soll)} Of brake caliper 2b of brake caliper 2b. The second target value (I _{2, soll)} is, the minute rotation of the direct current motor (2d) is realized under the action of the limited boosting brake pressure (P _u) by a minute rotation brake in the brake caliper (2b) side actuator (2c) of the brake piston. Even if the valve 7b and 8b follow the opening of the valve to reduce the pressure in accordance with step S7 ("P _u reduction"), the accumulated applied force F is maintained due to the irreversible transmission.

A second method for the hydraulic boosting of the electric parking brake of the rear wheels 12 starts according to Fig. 3 with steps S1 to S4 corresponding to the steps according to Fig. According to step S4, it does not reach the target force value (I _{1, soll)} corresponding to the actual value of the motor current (I _ist) a target force value (F _{1, soll)} that is, required application force (F _{1, soll} ) Is not set, similarly, hydraulic boosting is requested by the controller 20. For this purpose, following step S5 (generation of P _u ), the hydraulic boosting brake pressure P _u is controlled by the hydraulic pump 3 to the target pressure (P _{u , vor} ) corresponding to the target inlet pressure value P _{u ,} P _{u, soll} ), and the target inlet pressure value is smaller than the target force value (F _{1, soll} ). For example, for a target force value (F _{1, soll} ) of 140 bar, 80 bar may be selected as the target inlet pressure value ( _{Pu, vor} ).

The boosting brake pressure P _u corresponding to the target inlet pressure value P _{u , vor} is accumulated only in the brake piston of the brake actuators 2 c of the rear wheels 12. The hydraulic pump 3 continues to drive.

The brake pistons of the brake actuators 2c at the rear wheels 12 which receive the hydraulic brake pressure P _u are controlled by the displacement control using the displacement force characteristic stored in the controller 20 so that the brake piston of the brake actuators 2c, A further application is carried out in a subsequent step S6 ("additional application in displacement control for the target position of the brake piston") by driving to a position corresponding to the force value _{F1 , soll} .

Here, it starts from the position at the end of the application process according to step S3. Beginning at this stage, the displacement control uses a target position having a value slightly larger than the position at the end of the application process. For the target position, it is assumed that the brake calipers 2b are correspondingly given a larger force. The displacement controller is considered to want to adjust the brake position of the brake actuator 2c in the clamping direction to the target position in the clamping direction during the further application. Subsequent to said target position to achieve during the step S7 ( "reaches the target position"), is reduced in the hydraulic boosting brake pressure (P _u) The step S9 ( "P _u reduction"), that is, the hydraulic pump 3 is Shut off. In other cases, that is, when the target position is not reached, an error message for displaying to the driver is generated at step S8 ("error message display"), and the boosting brake pressure P _u is reduced at step S9.

The two methods of hydraulic boosting of the electrical parking brake described in conjunction with FIGS. 2 and 3 have the advantage that only a hydraulic boost is required or performed only when actually needed. In addition, as a result of the application process performed by the parking brake function according to step S3, since the brake piston of the brake actuator 2c has already been moved close to the required end position before the hydraulic boosting brake pressure is applied, The volume of the pressure medium produced by the pressure sensor 3 is very small.

Another advantage is that the method described above can also be used for further application of overheated parking brakes during the cooling phase.

The last exemplary embodiment of the method for hydraulic boosting of the electric parking brake according to Fig. 4 differs from the method according to Fig. 3 by the additional application function used.

For further application function, in step S6, the target value for the motor current (I) of the direct current motor _{(2d) (I 2, soll} ) is a first target power values used in the steps S3 and S4 (F _{1, soll)} with respect to the used as corresponding to the boosted brake pressure (P _{u, vor)} is reduced by the power value of the second target power value corresponding to the (F _{2, soll).} At this time, the boosted brake pressure (P _{u, vor)} brake piston of the brake actuator (2c) receiving has reached the target value (I _{2, soll)} the actual value of the motor current (I) (I _ist) or the target value Is applied by the controller 20 using the direct current motor 2d until it is exceeded; Thereafter, the direct current motor 2d is switched off.

The reduced target force value (I _{2 , soll} ) is also taken from the characteristic stored in the controller 20. These characteristic fields are determined for the defined hydraulic inlet pressures applied to the brake piston of the brake actuator 2c.

For the hydraulic inlet pressure between the feature values for a field it is present, and can be interpolated target values (I _{2, soll)} corresponding to the motor current (I).

If the target value (I _{2, soll)} is not reached by the motor current (I), according to the step S7 ( "error message display"), an error message is generated to the driver, according to the step S8 (P _u decreases) Following the reduction of the hydraulic boosting brake pressure P _u , the process is terminated (step S9: "end").

Before applying the addition of the parking brake according to the step S6, to the initial, brake actuator (2c) receiving the boosted brake pressure (P _u) is to achieve the defined for applying additional subsequent position, the parking brake by the displacement control It can be controlled by a minute displacement amount in a releasing direction.

The method finally described according to Fig. 4 also has the advantage that the hydraulic boost is performed only if this is actually necessary. Likewise, the volume supplied by the hydraulic pump 3 to the hydraulic boosting pressure is very small, since the brake piston of the brake actuator 2d has already moved close to the required end position according to step S3 and step S4.

1 Hydraulic brake system
2a brake caliper of the left front wheel 11
2b a brake caliper with a parking brake of the right rear wheel 12
2c < / RTI >
2d electric motor, a DC motor of the brake actuator 2c
3 Hydraulic pump
4 Electric motors for driving hydraulic pumps
5 Storage
6 switching valve
7a Inlet valve for brake caliper (2a)
7b Inlet valve for brake caliper (2b)
8a Outlet valve for brake caliper (2a)
8b Outlet valve for brake caliper (2b)
9 Brake master cylinder
10 Parking brake switch
11 Left front wheel
12 right rear wheel
13 Brake force booster
14 Low-pressure storage
15 Separation valve
16 Brake Pedal
20 DDC controller
21 DDC sensor system
I first brake circuit
II second brake circuit

Claims (13)

A method for hydraulic boosting of an electric parking brake of a vehicle comprising at least one brake actuator (2c, 2d)
The vehicle includes a hydraulic service brake function and an electrical parking brake function for electrical and hydraulic actuation of the at least one brake actuator (2c, 2d)
The application force F electrically generated by the electric parking brake function is generated by applying the brake actuators 2c and 2d to the hydraulic braking system by applying the hydraulic boosting brake pressure P _u provided by the hydraulic service brake function, Overlap with power,
During operation of the electric parking brake which generates a certain applied force, the applied force generated by the brake actuator (2c, 2d) is the actual value by the applied measured variable (I) representing the value of the force (I _ist ),
For an actual value (I _ist ) of the measured variable (I _ist ) smaller than a first target value (I _{1 , soll} ) indicative of a first target force value (F _{1, soll} ) of the applied force, the brake actuator , 2d receive the hydraulic boosting brake pressure P _u corresponding to the specified target boosting brake pressure value P _{u , soll} ,
By the electric parking brake function, an additional application function for further application of the brake actuators 2c, 2d receiving the hydraulic boosting brake pressure P _u is performed to realize the specified application force A method for hydraulic boosting of an electric parking brake of a vehicle. The method according to claim 1,
A method for hydraulic boosting of an electric parking brake of a vehicle, characterized in that means (3) for generating pressure are controlled by said hydraulic service brake function to produce said hydraulic boosting brake pressure (P _u ). 3. The method of claim 2,
The means (3) for generating the pressure comprises a hydraulic pump, a method for hydraulic boosting of an electric parking brake of a vehicle 3. The method of claim 2,
The target boosting brake pressure value (P _{u, soll} ) is set such that the resulting boosting brake force is set to a value corresponding to the first target force value (F _{1, soll} )
Following the generation of the hydraulic boosting brake pressure (P _u ) corresponding to the first target force value (F _{1, soll} ), the means (3) for generating the pressure is switched off,
Characterized in that the hydraulic boosting brake pressure (P _u ) applied to the brake actuators (2c, 2d) is hydraulically limited within the brake actuators (2c, 2d). 3. The method of claim 2,
Wherein the target boosting brake pressure value P _{u, soll} corresponds to a specified inlet pressure target value P _{u, vor} and the resulting boosting brake force is less than the first target force value F _1, ,
Following the generation of the hydraulic boosting brake pressure P _u , the means 3 for generating the pressure is not switched off and the brake actuators 2c, 2d generate the hydraulic boosting brake pressure P _u , Wherein the hydraulic braking system further comprises: 5. The method of claim 4,
_Wherein the actual value I _ist of the measurement variable I of the applied force is smaller than the first target value I ₁ corresponding to the first target force value F _1, for I _{2, soll)} further, the electric parking brake until respond to the application, wherein the brake actuator (2c, 2d) is that by the electric parking brake function, controlled by defined the hydraulic boosting brake pressure (P _u) ≪ RTI ID = 0.0 > 1, < / RTI > 6. The method of claim 5,
In order to further apply the electric parking brake by the electric parking brake function, displacement control is activated, and the brake piston of the brake actuator (2c, 2d) receiving the hydraulic boosting brake pressure (P _u ) wherein the target position is controlled to a target position corresponding to the specified applied force using a displacement-force characteristic. < Desc / Clms Page number 19 > 8. The method of claim 7,
Wherein an error message is generated if the target position with respect to the brake piston is not reached at the determined actual position. ≪ Desc / Clms Page number 21 > 6. The method of claim 5,
The additional application function of the brake actuators 2c and 2d includes the additional application of the brake actuator by means of the electric parking brake function whereby the brake actuators 2c and 2d, The actual value I _ist of the variable I is detected,
The additional application is terminated when the actual value I _ist of the measurement variable I reaches a second target value I _{2, soll} corresponding to the second target force value F ₂ ,
The second objective force value (F _{2, soll)} is a vehicle characterized in that the reduced relative to the first target force value (F _{1, soll)} by a value power corresponding to the hydraulic boosting brake pressure (P _u) A method for hydraulic boosting of an electric parking brake. 10. The method of claim 9,
_{, And an} error message is generated if the actual value (I _ist ) of the measured variable (I) does not reach the second target value (I _{2, soll} ). . 10. The method of claim 9,
Characterized in that the brake actuator (2c, 2d) receiving the hydraulic boosting brake pressure (P _u ) is controlled by a slight displacement amount in a direction of releasing the electric parking brake by displacement control before performing the additional application A method for hydraulic boosting of an electric parking brake of a vehicle. 12. The method according to any one of claims 1 to 11,
Characterized in that said hydraulic boosting brake pressure (P _u ) is reduced following the performance of said additional application function. 12. The method according to any one of claims 1 to 11,
In order to perform the electric parking brake function, the brake actuators 2c and 2d are driven by an electric motor 2d, and the motor current of the electric motor 2d is supplied as the measurement variable I Wherein the first and second control signals are detected.

Images